Portola Valley Weather
Town • San Francisco Bay Area
Portola Valley is a small, semi-rural town strung along Portola and Alpine roads. It fills the narrow valley that follows the San Andreas Fault between the foothills and Skyline Ridge. Windy Hill's bare summit rises straight above it to the west. The open space district's Windy Hill Preserve begins at a trailhead on Portola Road, and the Portola Trail links it to the Town Center. Oak woodland, horse properties and wooded canyons fill the rest of the valley, which is quieter and more enclosed than Woodside or Los Altos Hills on either side.
Plan your week
10-Day Forecast
Hour by hour
Hourly Forecast
Current Conditions
Comfort Breakdown
Portola Valley weather today and through the year
It's 53°F at Portola Valley right now (feels like 50°F), with 5 mph wind and a comfort score of 77. Monday's forecast high at Portola Valley is 56°F, 9°F below the mid November normal of 65°F. The best window today is 10 AM to 1 PM, at about 54°F with a 3 mph wind (comfort 57).
August is the warmest month at Portola Valley, with an average high of 81°F. December is the coldest, with an average low of 39°F. January is the wettest month (5.4 in.), out of about 27.0 in. a year. By typical temperature, wind, cloud, humidity, and rain odds, the most comfortable months at Portola Valley are September, July, and August. The best hours are usually 11 AM to 2 PM in September, 10 AM to 1 PM in July, and 10 AM to 1 PM in August.
The valley's shape drives the weather in Portola Valley. It is a long trough between Skyline Ridge and the lower foothills. On clear, calm nights, cold air drains off Windy Hill and the ridge and pools on the valley floor. Pilots who land there say valley temperatures occasionally drop below freezing at night. Winter mornings in town can be frostier than in Menlo Park or Palo Alto, just a few miles east.
Forecast updated November 15, 2026 at 4:00 AM PST. Climate figures come from NOAA 1991-2020 normals. Hourly patterns come from NOAA's HRRR hourly analysis from September 2014 to April 2026.
What to expect at Portola Valley in the next few days
No active National Weather Service alerts for this location.
Best time to go
The best window today is 10 AM to 1 PM, at about 54°F with a 3 mph wind (comfort 57).
Best day this week
Of the next 7 days, Friday looks best for Portola Valley, with a 59°F high and midday comfort near 73. Today looks weakest (45).
Rain
Next good chance of rain: today (84%, about 0.45 in.).
Live weather map
Weather around Portola Valley right now
Overcast and 53° at Portola Valley right now.
About the live weather map for Portola Valley
The map centers on Portola Valley and stacks fog, satellite clouds, and precipitation radar on one view. Clouds come from the GOES-West satellite and rain from NOAA radar, and both show current conditions. Fog comes from our HRRR-based fog model, and the slider steps through its forecast for the next 12 hours.
Dots mark nearby places with their current temperature, colored by comfort score. Use the layer buttons to turn any layer off, or open the full map for every destination in the region.
Nearby Temperature Comparison
Conditions at nearby San Francisco Bay Area destinations
Tip: Bay Area temperatures can change by 20 to 30°F over a short distance because of microclimates.
Portola Valley vs nearby places
Typical summer conditions compared with Portola Valley, from the same NOAA HRRR hourly record. The list shows the closest places, then nearby places whose climate differs the most.
| Place | Distance | Summer afternoons | Morning fog | Afternoon wind | Compared with Portola Valley |
|---|---|---|---|---|---|
| Windy Hill Open Space | 1.5 mi | -5°F | 34% | 11 mph | about 37% more rain a year and more summer morning fog (34% vs 21% of morning hours) |
| Woodside | 3.3 mi | +2°F | 17% | 8 mph | a very similar climate |
| Russian Ridge Open Space | 4.6 mi | -7°F | 36% | 9 mph | about 47% more rain a year and about 7°F cooler on summer afternoons |
| Montara | 18.9 mi | -21°F | 60% | 8 mph | about 21°F cooler on summer afternoons and more summer morning fog (60% vs 21% of morning hours) |
| Año Nuevo State Park | 19.2 mi | -20°F | 42% | 14 mph | about 20°F cooler on summer afternoons and more summer morning fog (42% vs 21% of morning hours) |
| Pacifica | 21.1 mi | -22°F | 56% | 9 mph | about 22°F cooler on summer afternoons and more summer morning fog (56% vs 21% of morning hours) |
Places with a climate like Portola Valley's
- American Canyon (55 mi away): nearly the same temperatures every month
- Sonoma (64 mi away): nearly the same temperatures every month
- Guerneville (88 mi away): nearly the same temperatures every month
Climate Dashboard
Current conditions vs. NOAA normals and recent destination baseline
What the Portola Valley climate comparisons mean
These cards compare recent conditions at Portola Valley with the available local baseline. Temperature and year-to-date rainfall use long-term normals when available. Fog, sunshine, wind, and comfort use the matching recent or modeled baseline identified on each card.
Positive and negative differences describe how Portola Valley departs from its own usual pattern. They should not be read as a direct comparison with another city or as a forecast beyond the period shown.
Portola Valley weather by month
August is the warmest month at Portola Valley, with an average high of 81°F. December is the coldest, with an average low of 39°F. January is the wettest month (5.4 in.), out of about 27.0 in. a year. Morning fog peaks in August, when fog or low cloud covers 26% of the hours from 6 to 10 AM. June has the clearest middays, with clouds covering about 15% of the sky from 11 AM to 3 PM.
By typical temperature, wind, cloud, humidity, and rain odds, the most comfortable months at Portola Valley are September, July, and August. The best hours are usually 11 AM to 2 PM in September, 10 AM to 1 PM in July, and 10 AM to 1 PM in August.
| Month | Avg high | Avg low | Rain | Rainy days | Morning fog | Midday cloud | Afternoon wind | Daylight | Comfort |
|---|---|---|---|---|---|---|---|---|---|
| Jan | 59°F | 40°F | 5.4 in | 10 | 14% | 34% | 6 mph | 9.9 h | 37 |
| Feb | 61°F | 41°F | 5.2 in | 10 | 10% | 27% | 8 mph | 10.8 h | 42 |
| Mar | 65°F | 43°F | 4.1 in | 8 | 8% | 32% | 8 mph | 11.9 h | 61 |
| Apr | 67°F | 44°F | 1.9 in | 6 | 9% | 26% | 9 mph | 13.2 h | 72 |
| May | 72°F | 48°F | 0.8 in | 4 | 12% | 26% | 10 mph | 14.2 h | 76 |
| Jun | 78°F | 51°F | 0.2 in | 2 | 15% | 15% | 9 mph | 14.7 h | 86 |
| Jul | 81°F | 53°F | 0.0 in | 0 | 21% | 15% | 8 mph | 14.5 h | 87 |
| Aug | 81°F | 54°F | 0.0 in | 1 | 26% | 16% | 8 mph | 13.6 h | 87 |
| Sep | 81°F | 52°F | 0.1 in | 1 | 19% | 18% | 8 mph | 12.3 h | 90 |
| Oct | 75°F | 48°F | 1.1 in | 4 | 13% | 18% | 7 mph | 11.1 h | 85 |
| Nov | 65°F | 43°F | 2.7 in | 7 | 11% | 24% | 6 mph | 10.1 h | 68 |
| Dec | 59°F | 39°F | 5.4 in | 10 | 17% | 36% | 6 mph | 9.6 h | 36 |
Morning fog is the share of hours from 6 to 10 AM with fog or low cloud. Midday cloud is the average from 11 AM to 3 PM, and afternoon wind is the average from 1 to 5 PM. The highlighted rows are the most comfortable months.
What makes Portola Valley's weather different
When the fog burns off
11 AMwhen August fog usually thins (35% foggy at 8 AM)
Fog or low cloud covers Portola Valley in 35% of 8 AM hours in August, the foggiest month. It usually thins to a third of that by 11 AM. March mornings are the least foggy (8%).
When the wind picks up
3 PMwhen afternoon wind builds, March–September
From March through September, wind at Portola Valley typically builds after 3 PM. In May it peaks around 6 PM, averaging 11 mph with 16% of those hours windy, while mornings average 7 mph.
Elevation
−7°Fsummer afternoons at Russian Ridge Open Space, 1,644 ft up
Russian Ridge Open Space sits 1,644 ft higher, 4.6 miles away. Its summer highs average 7°F cooler and its winter lows 1°F milder than Portola Valley.
Daylight
9.6–14.7 hof daylight, Dec to Jun
Days at Portola Valley range from about 9.6 hours in December to 14.7 hours in June. In mid-June the sun sets around 8:30 PM, and in mid-December around 4:57 PM.
Seasons at Portola Valley
- Warm seasonJun 30 – Sep 27 · highs 79°F+
The warm season lasts about 3 months, from Jun 30 to Sep 27, when the average high is 79°F or warmer. Highs peak around Aug 8 at about 81°F.
- Cool seasonNov 28 – Feb 28 · highs 63°F or lower
The cool season runs from Nov 28 to Feb 28, when the average high is 63°F or lower. The coldest nights come around Dec 8, with an average low near 39°F.
- Rainy seasonNov 6 – Apr 12 · 86% of the year's rain
The rainy season runs from Nov 6 to Apr 12, when a day has at least a 20% chance of measurable rain. That stretch brings 86% of the year's rain.
The dark line marks today. Season dates come from the smoothed daily NOAA 1991-2020 normals. Counting from Oct. 1, a typical year has its first inch of rain by Oct 28 and half of its annual total by Jan 25.
Days per year and extremes (Nov 1, 2024 to Oct 31, 2026)
This record runs from Nov 1, 2024 to Oct 31, 2026. Over this record, Portola Valley averaged 21 days a year at 90°F or hotter and no freezing nights. It averaged 14 days a year with at least half an inch of rain and 2 afternoons with wind of 20 mph or more at 2 PM. About 58 mornings a year had 3 or more hours of fog or low cloud.
In the same record, the hottest day was Sep 9, 2026 (100°F) and the coldest night was Jan 10, 2026 (36°F). The wettest day was Feb 5, 2025 (2.31 in.), and the strongest 2 PM gust was 50 mph on Feb 4, 2025.
- 21days at 90°F or hotter
- 0nights at or below freezing
- 14days with ½ in. of rain or more
- 2afternoons with 20+ mph wind
- 58mornings with 3+ hours of fog or low cloud
- Hottest day100°FSep 9, 2026
- Coldest night36°FJan 10, 2026
- Wettest day2.31 inFeb 5, 2025
- Strongest 2 PM gust50 mphFeb 4, 2025
What shapes Portola Valley's weather
Portola Valley's floor heats up on summer afternoons, shielded from the Bay breeze by the foothills and from the coast by Skyline Ridge. By late summer and fall the meadows send up thermals, rising columns of warm air, strong enough to bother paragliders landing near Windy Hill. Summer fog usually stays on the ridge above. On evenings when the cool ocean air is deep, it can spill over the crest toward town.
Winter storms drop more rain here than on the Bay plain, and the steep canyons and wooded slopes mean landslides and fallen trees are the usual storm damage. In March 2023 heavy rain triggered a 250-foot slide that closed Highway 84 near Portola Road in Woodside for months.
Oak woodland, chaparral and dry grass climb unbroken from the valley floor to Skyline, so fire weather matters here more than in the Bay plain towns. The riskiest days come in fall, when dry offshore winds replace the cool, moist ocean air.
Tips for visiting Portola Valley
Park at Town Center for Windy Hill
The Windy Hill lot on Portola Road fills quickly and street parking is enforced. Park at the Town Center, about 0.4 mile north, and walk the Portola Trail to the preserve.
Dress for cold mornings
Valley temperatures occasionally fall below freezing on clear nights, and low meadows stay wet and cold for days after winter rain.
Watch for storm road closures
Heavy rain can close mountain roads for months, including Highway 84, the key route to Skyline and the coast. Check road conditions before heading up after a big storm.
Sign up for SMC Alert
San Mateo County's opt-in alert system sends fire, flood and evacuation warnings. Add your address so alerts reach the right area.
Portola Valley through the seasons
- Spring (March–May)
- Spring brings green hills and wildflowers in the meadows around Sausal Pond. Days are mild, though mornings can still be cold on the valley floor.
- Summer (June–August)
- Summer brings warm, sunny afternoons in the sheltered valley and cool nights. Fog often sits on the ridge above town.
- Fall (September–November)
- Fall brings warm afternoons with strong thermals over the valley floor, and the highest fire danger of the year.
- Winter (December–February)
- Winter is rainy, with frost on some clear mornings between storms. Landslides and downed trees can close roads.
Activities and the weather that matters
- Hiking Windy Hill from town: Start early in summer. The climb from Portola Road to the summit is hot by afternoon and the top is often windy.
- Road cycling on Portola and Alpine roads: Popular valley loops are best mid-morning, after frost or chill lifts and before afternoon heat.
- Watching paragliders land: Pilots fly off Windy Hill when the wind is from the north-northeast to east-northeast and land in a field on the valley floor.
Official sources and current conditions
- Midpen: Windy Hill Preserve
- SMC Alert: San Mateo County emergency alerts
- Caltrans QuickMap: road conditions
Numbers on this page come from NOAA data. The text draws on the official sources linked above.
Historical Climate Data
Long-term weather patterns and climate data
Data sources: Recent temperatures come from NOAA URMA and recent precipitation from NOAA Stage IV. Fog, cloud, wind, humidity, and sunshine come from NOAA HRRR, and long-term baselines from NOAA 1991-2020 climate normals.
Climate Overview
Based on NOAA 30-year temperature/rain normals (1991-2020) with recent fog/sun baseline
🌟 Best Months to Visit
⚠️ Challenging Months
Monthly Breakdown
| Month | Comfort | High/Low | ☀️ Sun | 🌫️ Fog | 💧 Rain | Perfect |
|---|---|---|---|---|---|---|
| November 2024 | 83 | 62.8° / 46.4° | 6.9h | 0d | 3.15" | 23 |
| December 2024 | 75 | 61.3° / 46.5° | 5.8h | 7d | 5.45" | 13 |
| January 2025 | 84 | 60.3° / 42.5° | 7h | 3d | 0.13" | 23 |
| February 2025 | 77 | 61.3° / 44.3° | 6.9h | 3d | 8.26" | 17 |
| March 2025 | 82 | 61.8° / 44.8° | 8.8h | 2d | 3.17" | 18 |
| April 2025 | 90 | 67.8° / 46.3° | 9.8h | 4d | 0.6" | 24 |
| May 2025 | 93 | 75° / 48.8° | 12.2h | 1d | 0.18" | 31 |
| June 2025 | 95 | 77.4° / 50.5° | 12.7h | 3d | 0" | 30 |
| July 2025 | 93 | 78° / 53.2° | 12.3h | 4d | 0" | 31 |
| August 2025 | 90 | 84.2° / 55.5° | 11.5h | 6d | 0" | 29 |
| September 2025 | 90 | 80.8° / 58.1° | 9.7h | 4d | 0.12" | 28 |
| October 2025 | 89 | 73° / 52.1° | 7.8h | 4d | 0.6" | 25 |
| November 2025 | 78 | 64.7° / 48.8° | 6h | 8d | 3.48" | 14 |
| December 2025 | 72 | 58.4° / 44.2° | 5.6h | 8d | 5.18" | 9 |
| January 2026 | 81 | 62° / 45° | 6.7h | 3d | 5.47" | 23 |
| February 2026 | 80 | 63.7° / 46.9° | 7.1h | 3d | 2.75" | 19 |
| March 2026 | 95 | 77.2° / 51.5° | 9.8h | 0d | 0.01" | 31 |
| April 2026 | 89 | 67.5° / 47.9° | 9.7h | 0d | 1.82" | 24 |
| May 2026 | 91 | 72.4° / 50.4° | 11.7h | 3d | 0.38" | 31 |
| June 2026 | 94 | 78.1° / 53.5° | 12.5h | 0d | 0.01" | 29 |
| July 2026 | 93 | 80.8° / 54.5° | 11.8h | 1d | 0.02" | 30 |
| August 2026 | 91 | 81.2° / 55.6° | 11h | 7d | 0.04" | 31 |
| September 2026 | 93 | 80° / 54.2° | 10.4h | 1d | 0.04" | 28 |
| October 2026 | 89 | 77.8° / 53.1° | 8.3h | 1d | 0.05" | 27 |
Climate Trends
Average Temperature by Month
About the Portola Valley climate charts
The temperature chart compares average monthly highs and lows at Portola Valley, showing both the seasonal cycle and the typical day-to-night range. The comfort chart summarizes how often the combined weather pattern is favorable rather than judging temperature alone.
Precipitation shows the total recorded or modeled rainfall for each month at Portola Valley. Sunshine compares average bright-sky hours with the daylight available, while fog shows the average number of morning fog or low-cloud hours per day. Switch between the chart tabs to compare the same months across each measure.
Hourly Temperature, Fog, Wind, Cloud Cover, and Solar Radiation Patterns
Average local hour by month from 2014-09-30 to 2026-04-30
- Temperature: At Portola Valley, the warmest typical hour is 3 PM in August (81°F). The coldest is 7 AM in December (46°F).
- Fog: Fog or low cloud covers Portola Valley in 35% of 8 AM hours in August, the foggiest month. It usually thins to a third of that by 11 AM. March mornings are the least foggy (8%).
- Wind: From March through September, wind at Portola Valley typically builds after 3 PM. In May it peaks around 6 PM, averaging 11 mph with 16% of those hours windy, while mornings average 7 mph.
- Cloud Cover: June middays are the clearest at Portola Valley (15% average cloud cover), and December middays are the cloudiest (36%).
- Solar Radiation: The strongest typical sun at Portola Valley comes at 1 PM in June, averaging 986 W/m².
How to read the hourly heatmaps for Portola Valley
This heatmap shows how average temperature at Portola Valley changes by hour and month. Read left to right for the seasons and top to bottom for the time of day. Warmer colors mark the usual afternoon peaks, and cooler colors show overnight and winter lows.
This heatmap shows when fog or low cloud is most likely at Portola Valley. Darker cells mark the months and hours when fog has been most common. They help separate overnight or morning fog from cloud that tends to linger into the afternoon.
This heatmap shows the typical hourly wind pattern at Portola Valley through the year. It makes recurring afternoon wind, calmer overnight periods, and seasonal changes easier to compare than a single daily wind value.
This heatmap shows average cloud cover at Portola Valley for every month and hour. Use it to see whether cloudiness is mainly an overnight and morning pattern or commonly persists during the part of the day you plan to visit.
This heatmap shows the average solar radiation reaching Portola Valley by month and hour. Brighter cells indicate the strongest typical sun, while muted cells can reflect nighttime, shorter winter days, cloud cover, smoke, or terrain shading.
Each cell combines one month with one local hour. Hover over or focus on a cell for its value and sample coverage. The red marker shows the current month and hour.
How recent months compared at Portola Valley
- October 2026 recap: October 2026 at Portola Valley averaged a high of 78°F, 3°F warmer than the 1991-2020 normal of 75°F. It brought 0.05 in. of rain, compared with a normal of 1.12 in.
- Rain year: The 2025-26 rain year (Oct. 1 to Sep. 30) brought 19.8 in. of rain to Portola Valley, 73% of the 27.0 in. normal.
Location Details
Portola Valley weather questions
Everything you need to know about weather and visiting Portola Valley
What is the weather like at Portola Valley today?
It's 53°F at Portola Valley right now, with a comfort score of 77 (great). Monday's forecast high at Portola Valley is 56°F, 9°F below the mid November normal of 65°F. The best window today is 10 AM to 1 PM, at about 54°F with a 3 mph wind (comfort 57).
What is the best month to visit Portola Valley?
By typical temperature, wind, cloud, humidity, and rain odds, the most comfortable months at Portola Valley are September, July, and August. The best hours are usually 11 AM to 2 PM in September, 10 AM to 1 PM in July, and 10 AM to 1 PM in August. The warm season lasts about 3 months, from Jun 30 to Sep 27, when the average high is 79°F or warmer. Highs peak around Aug 8 at about 81°F.
What are the warmest and coldest months at Portola Valley?
August is the warmest month at Portola Valley, with an average high of 81°F. December is the coldest, with an average low of 39°F.
When does the fog burn off at Portola Valley?
Fog or low cloud covers Portola Valley in 35% of 8 AM hours in August, the foggiest month. It usually thins to a third of that by 11 AM. March mornings are the least foggy (8%).
When is it windiest at Portola Valley?
From March through September, wind at Portola Valley typically builds after 3 PM. In May it peaks around 6 PM, averaging 11 mph with 16% of those hours windy, while mornings average 7 mph.
How much rain does Portola Valley get?
January is the wettest month (5.4 in.), out of about 27.0 in. a year. The rainy season runs from Nov 6 to Apr 12, when a day has at least a 20% chance of measurable rain. That stretch brings 86% of the year's rain. The 2025-26 rain year (Oct. 1 to Sep. 30) brought 19.8 in. of rain to Portola Valley, 73% of the 27.0 in. normal.
How does Portola Valley weather compare with Russian Ridge Open Space?
Russian Ridge Open Space sits 1,644 ft higher, 4.6 miles away. Its summer highs average 7°F cooler and its winter lows 1°F milder than Portola Valley.
What kind of place is Portola Valley?
Portola Valley is a small, semi-rural town strung along Portola and Alpine roads. It fills the narrow valley that follows the San Andreas Fault between the foothills and Skyline Ridge. Windy Hill's bare summit rises straight above it to the west. The open space district's Windy Hill Preserve begins at a trailhead on Portola Road, and the Portola Trail links it to the Town Center. Oak woodland, horse properties and wooded canyons fill the rest of the valley, which is quieter and more enclosed than Woodside or Los Altos Hills on either side.
What is Portola Valley weather like in November?
November at Portola Valley averages a high of 65°F and a low of 43°F, with 2.7 in. of rain over about 7 rainy days. About 11% of morning hours are foggy. Afternoon wind averages 6 mph.
More about Portola Valley weather
Guides that explain the weather here and nearby
Data sources and methods
- Monthly temperatures and precipitation: NOAA 1991-2020 normals.
- Fog, cloud, wind, sun, and comfort by hour and month: NOAA's HRRR hourly analysis from September 2014 to April 2026.
- Daily records and recent months: NOAA URMA and HRRR analyses, plus NOAA Stage IV precipitation.
- Nearby comparisons and regional rankings use the same hourly HRRR summaries for every destination in the region.
- Alerts: National Weather Service. Tides and ocean temperature: NOAA CO-OPS, where shown.
- All statements on this page are computed from these datasets, apart from the “What shapes the weather” guide, which cites its sources inline.
- Midpeninsula Regional Open Space District, Windy Hill Preserve (accessed 2026-10-27)
- Wings of Rogallo, Windy Hill site guide (updated Feb 19, 2026) (accessed 2026-10-27)
- The Almanac, Caltrans: Landslide-damaged section of Highway 84 in Woodside won't fully reopen until December or later (Sept 1, 2023) (accessed 2026-10-27)
- San Mateo County Department of Emergency Management, SMC Alert (accessed 2026-10-27)
Rendered 2026-11-15T12:16:30.963Z.